Soaps are made by reacting fats or oils with a strong alkali like sodium hydroxide. Detergents are similar cleansing agents but use synthetic surfactants instead of fats/oils and do not form scum with hard water. The manufacturing process for soaps involves saponification of fats/oils, glycerin removal, purification, and finishing. Detergent production uses petrochemical raw materials and involves slurry making and spray drying. Both have advantages like cleaning ability but can harm aquatic environments if not properly treated in wastewater.

1. “Soaps and Detergents”

2. Soap
Definition:
Soaps are water soluble sodium or potassium salts of fatty acids.
Soaps are made from fats and oils, or their fatty acids, by treating
them chemically with a strong alkali.
OR
Soap is a cleansing agent created by the chemical reaction of a
fatty acid with an alkali metal hydroxide. Soap has general
chemical formula “RCOOX”.

3. Raw Material:
1) Fats and Oils: Fats & Oil are used in soap-making come
from animal or plant sources. Each fat or oil is made up of a
distinctive mixture of several different triglycerides.
In a triglyceride molecule, three fatty acid molecules are attached
to one molecule of glycerine. There are many types of
triglycerides; each type consists of its own particular combination
of fatty acids. Fatty acids are the components of fats and oils that
are used in making soap. They are weak acids composed of two
parts: A carboxylic acid group consisting of one hydrogen (H)
atom, two oxygen (O) atoms, and one carbon (C) atom, plus a
hydrocarbon chain attached to the carboxylic acid group.
Generally, it is made up of a long straight chain of carbon (C)
atoms each carrying two hydrogen (H) atoms.
2) Alkali:
• An alkali is a soluble salt of an alkali metal like sodium or
potassium. Originally, the alkalis used in soap-making were
obtained from the ashes of plants, but they are now made
commercially. Today, the term alkali describes a substance
that chemically is a base (the opposite of an acid) and that
reacts with and neutralizes an acid.
• The common alkalis used in soap-making are sodium
hydroxide (NaOH), also called caustic soda; and potassium
hydroxide (KOH), also called caustic potash.

4. Soap Manufacturing Process
Soaps are the product of the reaction between a fat and
sodium hydroxide.
fat + 3NaOH → glycerine + 3 soap
Soaps are produce industrially in four basic steps.
1. Saponification
The chemical reaction between any fat and sodium hydroxide
is a saponification reaction.
OR
The process of making soap by the hydrolysis of fats and oils with
alkalies.
In saponification, a mixture of tallow (animal fat) and coconut oil is
mixed with sodium hydroxide and heated. The soap produced is
the salt of a long chain carboxylic acid.
2. Glycerine Removal
Glycerine is more valuable than soap, so most of it is removed.
Some is left in the soap to help make it soft and smooth. Soap
is not very soluble in salt water, whereas glycerine is, so salt is

5. added to the wet soap causing it to separate out into soap
and glycerine in salt water.
3. Soap Purification
Any remaining sodium hydroxide is neutralized with a
weak acid such as citric acid and two thirds of the
remaining water removed.
4. Finishing
Additives such as preservatives, colour and perfume are
added and mixed in with the soap and it is shaped into
bars for sale.

6. Process Flow Chart

7. ANCILLIARY PROCESSES
Glycerine Recovery
As has already been stated, glycerine is more valuable
than the soap itself, and so as much of it as possible is
extracted from the soap. This is done in a three step
process.
Step: 1 - (Soap Removal)
The spent lye contains a small quantity of dissolved
soap which must be removed before the evaporation
process. This is done by treating the spent lye with ferrous
chloride.
Step: 2 - (Salt Removal)
Water is removed from the lye in a vacuum
evaporator, causing the salt to crystallize out as the
solution becomes supersaturated. This is removed in a
centrifuge, dissolved in hot water and stored for use as
fresh lye. When the glycerine content of the solution
reaches 80 - 85% it is pumped to the crude settling tank
where more salt separates out.

8. Step: 3 - (Glycerine Purification)
A small amount of caustic soda is added to the crude
glycerine and the solution then distilled under vacuum in a
heated still. Two fractions are taken off - one of pure
glycerine and one of glycerine and water. The glycerine
thus extracted is bleached with carbon black then
transferred to drums for sale, while the water/glycerine
fraction is mixed with the incoming spent lye and repeats
the treatment cycle.

9. Classification of Soap
• Run and Glued Up Soaps
• Curd Soap
• Sulphur Soap
• Tar Soap
• Carbolic Soap
• Peroxide Soap
• Mercury Soap
• Castile Soap
• Transparent Soap
• Shaying Soap
• Pumice/ Sand Soap
• Liquid Soap
• Textile Soap.

10. Advantages & Disadvantages of Soap
Advantages:
• Very effective as a bactericide.
• It will form gels, emulsify oil and lower the surfaces
tension of water.
• Excellent everyday cleaning agent.
• Good biodegradability
Disadvantages:
• Oils and perfume are immiscible in water and if spilled
create havoc, although the oils do solidify at room
temperature.
• When used in hard water, soap can produced a scum.
Note:- Soaps, will react with metal ions in the water
and can form insoluble precipitates (soap scum).

11. Detergents
Definition:
A water-soluble cleansing agent which combines with
impurities and dirt to make them more soluble, and
differs from soap in not forming a scum with the salts
in hard water.
OR
• Detergents are the sodium salts of long chain benzene
sulphuric acids.
• It is used in both, Powder and Liquid form, and sold as
laundry powders, hard surface cleansers, dish
washing liquids, fabric conditioners etc.

12. Raw Material
Petrochemicals are utilized as a raw material for the
manufacturing of detergents.
Explanation:
Primarily surfactants, which could be produced easily
from petrochemicals. Surfactants lower the surface
tension of water, essentially making it 'wetter' so that it
is less likely to stick to itself and more likely to interact
with oil and grease.
(SURFACTANTS - SURFACE ACTIVE AGENTS)

13. Detergent Manufacturing Process
• Step 1 - Slurry Making
The solid and liquid raw ingredients are dropped into
a large tank known as a slurry mixer. As the ingredients
are added the mixture heats up as a result of two
exothermic reactions: the hydration of sodium
tripolyphosphate and the reaction between caustic soda
and linear alkylbenzenesulphonic acid. The mixture is then
further heated to 85oC and stirred until it forms a
homogeneous slurry.
• Step 2 - Spray Drying
The slurry is deaerated in a vacuum chamber and then
separated by an atomiser into finely divided droplets.
These are sprayed into a column of air at 425 C, where
they dry instantaneously. The resultant powder is known
as 'base powder', and its exact treatment from this point on
depends on the product being made.

14. • Step 3 - Post dosing
Other ingredients are now added, and the air
blown through the mixture in a fluidiser to mix them into a
homogeneous powder. Typical ingredients are listed in the
following table.

15. Process Flow Chart

16. Advantages & Disadvantages of Detergent
Advantages:
• Biodegradable .
• Detergents do not decompose in acidic medium.
• As detergents are derived from petroleum they save
on natural vegetable oils.
Disadvantages:
• Their elimination from municipal wastewaters by the
usual treatments is a problem.
• It has tendency to produce stable foams in rivers that
extend over several hundred meters of the river water.
• It is dangerous to aquatic life.
• Some surfactants are incompletely broken down with
conventional treatment processes
• It an inhibitor oxidation.
Wastes:
• Phosphate Builders
• Excess of detergent foam
• Effluent
• Excess chemicals

17. Soap & Detergents Products
Four General Categories:
• Personal Cleansing – include bar soaps, gels, liquid
soaps and heavy duty hand cleaners.
• Laundry – available as liquids, powders, gels, sticks,
spray pumps, sheets and bars
Personal Cleansing laundry
dishwashing Household Cleaning

18. • Dishwashing – include detergents for hand and
machine dishwashing as well as some specialty
products. (liquids, gels, powders, solids)
• Household Cleaning – available as liquids, gels,
powders, sheets and pads for use on painted, plastic,
metal, porcelain, glass and other surfaces, and on
washable floor coverings.